This invention relates to cushioning articles which are suitable for seat pads in various vehicles and furniture such as sofas and beds, and to a process for producing the same.
As cushioning articles to be used in furniture such as beds and vehicle seats, there are known integrally molded articles made of foamed RIM (Reaction Injection Molding) urethane, waddings of nonelastic crimped fibers such as polyester and fibrous cushioning articles formed by bonding nonelastic crimped fibers with binders. Among all, foamed RIM urethane is widely used in, for example, vehicle seats because of the high settling resistance and favorable processing characteristics thereof.
However, the foamed RIM urethane has a crosslinked structure, which brings about a problem that it is hardly recyclable. In the disposal of the foamed RIM urethane, moreover, there arises another problem to be solved that toxic cyanogen gas is generated in the combustion thereof. The foamed RIM urethane suffers from an additional problem that it has only an insufficient air-permeability and thus imparts a stuffy feel in prolonged use.
On the other hand, cushioning articles made of thermoplastic fibers are disclosed in, for example, JP-A-7-243163 (The term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d), JP-A-7-238461, JP-A-7-238462, JP-A-7-324271, JP-A-8-10470, JP-A-8-124068 and JP-A-8-56772. These cushioning articles are excellent in air-permeability owing to the three-dimensional network structure of the fibers. Because of being made of thermoplastic materials, these cushioning articles have another advantage of being recyclable. In the three-dimensional network structure of these cushioning articles, however, the fusion strength of the fibers is still insufficient and thus only poor settling resistance can be achieved when processed into cushions. In addition, there arises another problem that uniform cushioning articles can be hardly obtained because of the insufficient steric regularity thereof. Furthermore, these cushioning articles are less uniform, which makes them inferior in comfortableness in sitting on to the existing foamed and crosslinked urethane.
JP-A-8-61410 discloses a process of using thermoplastic fibers and foaming the same. In this process for producing the foamed fibers, unfoamed fibers are extruded into a mold and then foaming is carried out in another step. As a result, not only troublesome procedures but much energy are needed for the latter step of heating. Similar to the non-foamed fiber cushioning articles as described above, the foamed fibers thus obtained have insufficient fusion strength and thus only poor settling resistance can be achieved when processed into cushions. In addition, there arises another problem that uniform cushioning articles can be hardly obtained because of the insufficient steric regularity thereof. Since the foaming is performed in the latter step, moreover, the voids among fibers have only a small volume and thus the apparent density of the cushioning articles is enlarged, which results in another problem that the cushioning articles are poor in softness.
An object of the invention is to provide a process for producing a cushioning article which has good air-permeability, excellent settling resistance and favorable softness.
Another object of the present invention is to provide a cushioning article molded by the production process.
Other objects and effects of the present invention will become apparent from the following description.
The above-described objects of the present invention have been achieved by providing the following production processes and cushioning article.
(1) A process for producing a cushioning article, which comprises:
providing an injection molding apparatus having plural injection orifices, said orifices each having a discharge angle from 5xc2x0 to 45xc2x0 inclining from the vertical direction;
injecting a thermoplastic polymer material in the form of strand from said plural orifices into a mold; and
cooling said mold followed by demolding.
(2) The production process according to item (1) above, wherein the discharge angles of said orifices as projected into a horizontal plane each has a phase difference of from 5xc2x0 to 120xc2x0 relative to those of adjacent orifices.
(3) The production process according to item (1) or (2) above, wherein said thermoplastic polymer material contains a foaming agent.
(4) The production process according to any one of items (1) to (3) above, wherein said thermoplastic polymer material comprises a thermoplastic elastomer.
(5) The production process according to item (4) above, wherein said thermoplastic elastomer is a polyester-based elastomer or a polyurethaner-based elastomer.
(6) A cushioning article molded by a production process according to any one of items (3) to (5) above, having an expansion ratio of from 1.0 to 4.0, a strand sectional area of from 0.2 to 25.0 mm2 and an apparent density of the cushioning article of from 0.005 to 0.24 g/cm3.